How is flexion during labor defined?

Updated: Jan 24, 2019
  • Author: Sarah Hagood Milton, MD; Chief Editor: Christine Isaacs, MD  more...
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As the fetal vertex descents, it encounters resistance from the bony pelvis or the soft tissues of the pelvic floor, resulting in passive flexion of the fetal occiput. The chin is brought into contact with the fetal thorax, and the presenting diameter changes from occipitofrontal (11.0 cm) to suboccipitobregmatic (9.5 cm) for optimal passage through the pelvis.

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